Icebergs in Lake Michigan sometimes have stripes, formed by layers of snow that react to different conditions.
Blue stripes are often created when a crevice in the ice sheet
fills up with melt water and freezes so quickly that no bubbles form. When an iceberg falls into the lake, a layer of water can freeze to the underside. If this is rich in algae, it can form a green stripe. Brown, black and yellow lines are caused by sediment, picked up when the ice sheet grinds downhill towards the lake.
